1. Field of the Invention
The present invention relates to a polyamide composite material containing an organized clay, and a production method thereof, and more particularly to a polyamide composite material comprising a specific organized clay and polyamide, which is excellent in gas barrier properties and transparency, and a production method of the polyamide composite material.
2. Description of the Prior Art
Polyamides have been widely used not only as injection-molding materials for automotive, electric and electronic parts, but also as packaging materials for foodstuffs, beverages, drugs and electronic parts, because of their excellent mechanical properties and processability as well as relatively high gas barrier properties. Among the polyamides, poly(m-xylylene adipamide) produced by the polycondensation of a diamine component mainly composed of m-xylylenediamine and a dicarboxylic acid component mainly composed of adipic acid (hereinafter occasionally referred to merely as “nylon MXD6”) exhibits a low permeability against gaseous substances such as oxygen and carbon dioxide as compared to other polyamides, and therefore, has now come into use as packaging materials requiring gas barrier properties such as films and bottles. In recent years, there is a strong demand for packaging materials capable of keeping freshness of foodstuffs, beverages, etc., for a prolonged period of time. Therefore, the nylon MXD6 has been required to have further enhanced gas barrier properties.
One of the methods for enhancing the gas barrier properties of polyamides is to uniformly disperse phyllosilicate in a polyamide thereby to prepare a polyamide composite material (for example, Japanese Patent Application Laid-Open No. 62-74957). Japanese Patent Application Laid-Open No. 9-217012 discloses a method of producing a polyamide composite material comprising a polyamide having phyllosilicate uniformly dispersed therein by melt-kneading the polyamide and the phyllosilicate in a twin-screw extruder. The proposed methods requires to apply a strong shear force to a mixture of the nylon MXD6 and the organized clay by the rotation of a screw in the melt-kneading process. The heat generated by the shearing decomposes the organizing agent in the organized clay to allow the agglomeration of the clay. Therefore, the clay fails to be completely and finely dispersed and/or distributed in the polyamide to result in the failure in improving the gas barrier properties. In addition, there occur problems such as deterioration in transparency, increase in YI and malodor development due to decomposition of the organizing agent.